In an existing wet etching apparatus, in order to improving uniformity of wet etching on a large-area to-be-processed substrate, the to-be-processed substrate is generally placed inclined, such that etchant on the to-be-processed substrate can flow along a surface of the to-be-processed substrate under gravity to maintain a good liquid exchange rate, so as to avoid non-uniform etch rate due to stagnation of the etchant on the to-be-processed substrate.
However, in practice, it is found that, in an area at a lower position of the to-be-processed substrate, both the sprayed etchant and the etchant flowing from a higher position are gathered, thus a phenomenon of etchant accumulation may occur in the area at the lower position of the to-be-processed substrate, which results in a relatively low etchant flowing exchange efficiency in this area, and in turn results in a relatively low etch rate in the lower position (because the etchant flowing exchange efficiency is in direct proportion to the etch rate). In the meantime, since the phenomenon of etchant accumulation does not occur in an area at a higher position of the to-be-processed substrate, the etch rate is normal in the higher position.
It can be seen from the above that the wet etching in an inclined manner in the prior art still suffers from the problem of non-uniform etch rate.